This invention relates generally to methods and apparatus relating to x-ray imaging systems, and more particularly to methods and apparatus for adjusting focal spot positioning and collimation relative to a target within an imaging tube.
A collimator in a computed tomographic system is a mechanical device that forms a beam for various slice thicknesses. In various configurations, a collimator is used to maintain a proper aperture to minimize radiation dose to a patient. Also in some configurations of CT, the size and position of the focal spot of the radiation beam is dynamically controllable. In particular, modulating focal spot position in an x-direction enables “focal spot wobble,” which improves image quality.
At least one known collimator configuration is suitable for forming x-ray beams in VCT systems having coverage of up to about 20 mm at isocenter. However, newer VCT system coverage is expected to increase to between about 20 and 200 mm. Collimator designs suitable for such large system coverage, combined with z-axis tracking requirements, would be both complicated and expensive.